Method and Apparatus for Establishing Resource Pool for Scheduling Assignment Signal of Direct Device-To-Device Communication in Wireless Communication System

1. A method for transmitting scheduling assignment (SA) for device-to-device (D2D) communication by a user equipment (UE) in a wireless communication system, the method comprising: determining whether data to be transmitted is present using the D2D communication; determining whether the SA is transmitted according to a resource allocation mode for the D2D communication when the data is not present; and transmitting first SA when the resource allocation mode is a first mode, wherein the resource allocation mode comprises the first mode in which resource for the D2D communication is allocated by a base station and a second mode in which resource for the D2D communication is allocated according to arbitrary selection of the UE.

2. The method according to claim 1 , further comprising transmitting second SA comprising information on resource for transmission of the data when the data is present, wherein the second SA comprises information on an identifier of a reception UE.

3. The method according to claim 2 , wherein the first SA comprises information indicating that data transmission corresponding to the first SA is not present.

4. The method according to claim 2 , wherein the second SA is repeatedly transmitted in a plurality of time resources and the first SA is transmitted one time in one time resource.

5. The method according to claim 1 , wherein the UE does not transmit SA when the resource allocation mode is the second mode.

6. The method according to claim 1 , further comprising transmitting dummy data through resource indicated by the first SA when the first SA is transmitted.

7. The method according to claim 1 , wherein the determining of whether the SA is transmitted comprises: driving a predetermined timer upon determining that the data is not present; and determining whether the SA is transmitted according to a resource allocation mode for the D2D communication when the timer does not expire, wherein the UE does not transmit SA when the timer expires.

8. A method of transmitting scheduling assignment (SA) for device-to-device (D2D) communication by a user equipment (UE) in a wireless communication system, the method comprising: determining whether SA is transmitted in a previous SA period; determining whether resource for a data channel in a current SA period is changed when the SA is transmitted in the previous SA period; and transmitting the SA using resource of a first SA resource pool when the resource for the data channel is not changed, wherein, when the SA is not transmitted or the resource for the data channel is changed in the previous SA period, the SA is transmitted using resource of a second SA resource pool.

9. The method according to claim 8 , further comprising transmitting the SA indicating termination of transmission of the data channel using the resource of the second SA resource pool when the transmission of the data channel is terminated.

10. The method according to claim 8 , wherein the SA comprises information on whether the resource for the data channel is changed in a next SA period.

11. The method according to claim 8 , wherein the SA comprises information on the number of SA periods in which the resource for the data channel is not changed.

12. The method according to claim 8 , wherein the number of resources included in the second SA resource pool is greater than the number of resources included in the first SA resource pool.

13. The method according to claim 8 , wherein the first SA resource pool precedes the second SA resource pool in a time region.